Preselective tuning mechanism for radio receiving systems and the like



March 18, 1941. BELL, Q 72 235195 PRESELECTIVE TUNING MECHANISM FOR RADIO RECEIVING SYSTEMS 'AND THE LIKE Filed Jan. 4, 1939 lllllllllfml g INVETOR 94m? mar/m nu ATTORNEY Patented Max:218, 1941 UNITED STATES PRESELECTIVE TUNING MECHANISM FOR RADIO RECEIVING SYSTEMS AND THE LIKE David Arthur Bell, Chelmsford, England, assignor to Radio Corporation of America, a corporation of Delaware Application January 4, 1939, Serial No. 249,197 In Great Britain January. 22, 1938 Claims.

This invention relates to preselective tuning mechanism for radio receivers and the like, that is to say, to tuning mechanism whereby anydesired one of a predetermined plurality of tuning 5 settings can be obtained by merely pressing an appropriately marked key or pushing an appropriately marked button so that the operation of tuning the receiver calls for no skill on the part of the operator. The invention provides improved preselective tuning mechanisms of the i kind wherein any desired one of a predetermined plurality of positions of a tuning member, usually the shaft of a tuning condenser or condenser gang, can be selected merely by operating the appropriate key or button.

The main object of the invention is to provide improved preselective tuning mechanisms of the kind in question wherein there is no need for any re-set key, one tuning settingafter another being automatically obtainable merely by pressing one key or button after another.

A further object of the invention is to provide improved preselective tuning mechanism of the kind referred to wherein the predetermined tuning positions are easily adjustable either in manufacture or otherwise.

A still further objectof the invention is to provide improved preselective tuning mechanism of the kind referred to wherein the operator may, if and when he so desires, tune the set in the ordinary way by operation of a manual tuning knob.

According to this invention a preselective tuning mechanism for a radio receiver or the like comprises a plurality of abutment members fast with the tuning member of the receiver, a plurality of cooperating stop members individually movable into and out of the paths of said abutment members, said stop members and abutment members being in such mutual relationship that the permissible movement of the tuning member away from a datum position can be selected at any of a plurality of predetermined amounts by selecting an appropriate stop member to be moved into the path of its cooperating abutment member, means for biasing said tuning member away from said datum position, selector members for selecting any stop member to be moved into the path of the cooperating stop member, means actuated upon operation of any of the selector members for moving said tuning member to its datum position and then releasing it to move under its bias until it is stopped by the selected stop member, and means for retainingany abutment member and cooperating stop member which have engaged one another in such engagement until a fresh tuning operation is initiated.

Preferably ordinary manual control means for the tuning member is provided so as to permit of the use of ordinary tuning when desired. 5

Preferably also means are provided for automatically maintaining the receiver inoperative to reproduce while a tuning operation is in progress.

Tho-ugh not limited to its application thereto the invention is particularly well adapted to application to radio receivers embodying socalled automatic frequency control, that is to say, to radio receivers having means whereby once the receiver is tuned within a predetermined degree of accuracy to an incoming station, it automatically pulls into corrct tune and maintains itself so tuned. When the invention is applied to such a receiver it will be appreciated that slight errors in the individual tuning settings selectable by the preselective mechanism become of minor importance because, so long as the preselective mechanism is capable of tuning the receiver fairly closely to the appropriate stations, the automatic frequency control system will take charge and obtain and maintain accurate tuning.

The invention is illustrated in the accompanying drawing which shows schematically one way of carrying out this invention as applied to a receiver wherein the tuning member is a rotary condenser shaft, Fig. 1 being an end view of the mechanism and Fig. 2 a side view of that part of the mechanism which revolves with the said condenser shaft. 35

Referring to the drawing the condenser shaft l is rotatable over a predetermined angle of rotation limited at both ends by fixed stops as in the usual way and on this shaft is keyed a concentric drum 2. Helically arranged along the periphery of the drum is a plurality of abutment members. Only the first and last of these abutment members have been shown. These two abutment members are generally designated 3 and 4 respectively. The other, intermediate 45 abutment members are spaced along the helical path represented by the broken lines HP in Fig.

2. Each abutment member is in the form of a screw 5 which is tangential to or parallel to a tangent to the drum 2 and is carried in a 50 bracket 6 fixed to or formed on the drum 2. For example, the brackets 6 may be constituted as shown by tongues punched from the sheet metalconstituting the curved surface of the drum and bent up at right angles thereto leaving 55 -.will generally be regarded as permissible.

a slot 8 in the drum surface behind each bracket. Each screw 5 may be fitted with a lock nut I or alternatively some suitable cement, such as shellac, wax, or Celluloid solution, may be arranged to fix each screw in a desired position of adjustment. A plurality of pivoted stop members 9 is provided, there being one stop member for each abutment member, the ends of all the stop members being in a line parallel to the axis of the drum 2. The arrangement is such that each stop member is individually movable into or out of the path of the abutment member with which it is associated and is biased out of said path by a spring or, as shown, by a weight [0. The stop members may all be pivoted on a common shaft or spindle ll parallel to the axis of the drum. The radius adopted for the drum (measured from the shaft of the abutment members) depends upon the accuracy of tuning required. For example, in the case of a broadcast receiver having automatic frequency control a tolerance of 3 k. c. on the medium wave band The accuracy of setting would then have to be 3 parts in 1,000 for a range of 500 k. c. to 1500 k. c. (assuming the tuning system to be such that the frequency is rectilinearly proportional to angular rotation of the tuning shaft) and assuming a drum of 3" radius this would mean a tolerance of the order of an inch, quite a generous tolerance. Moreover, individual fine adjustment is easily obtainable by screwing the screws 5 in and out of the brackets 6.

The tuning shaft is spring biased in such direction that it tends to rotate to bring the abutment members against the stop members and the extreme position of the tuning shaft in a direction opposite to the direction of spring bias is the position herein termed the datum position. In the construction illustrated the spring bias is provided by a tension spring l3 acting through a flexible cord l2 which is wrapped round the drum and anchored thereto at the end He. Of course, other methods of spring bias could be used; for example, a coiled spring could be provided on the shaft with one end anchored to the shaft and the other to a fixed point or a spring could be provided to act on the rack I! to be referred to later.

A plurality of operating keys 14, corresponding in number to the plurality of abutment members and stop members, is provided. Each key, which may be marked with the name of a transmitting station or other means of identifying the tuning position to which it corresponds is mounted on the end of an operating lever I411. pivoted at 3| and spring biased by a tension spring 23. Each operating lever has pivotally attached thereto a member I50. with an upper arm l5 shaped to engage the upper face of a bar l6 which runs the length of the mechanism and is attached to the lower end of a rack l1 engaging a pinion l 8 on the shaft l. Thus, depression of a key M pulls down member l5a and by engagement of l5 and I6, pulls down the rack l I and rotates the shaft I and drum 2 to the datum position. Each member I 50. is formed with a cam face 19 and it will be seen that as the member |5a comes down, the cam l9 engages a roller 20 and forces back the member [5a against the bias of a spring 2|, as indicated by the arrow in Fig. 1. As a result the part l5 disengages from I6, the rack is released and the drum 2 and shaft l rotate (clockwise in Fig. 1) under the bias of the spring l3. Simultaneously, the forcing back of member l5a causes the rear face of this member to engage a strip 22 which rotates stop member 9 on its pivot H against the bias of weight'l0 so that the end of the said stop member is moved into the path of the appropriate screw 5 and will be engaged thereby when the spring l3 has rotated the drum 2- far enough.

The stop member 9 is suitably recessed at its end to receive the appropriate screw 5, so that once the said screw is engaged in said recess it will remain therein after the operating key I4 is released. When the key M is released, since part I5 is now below part IS, the key cannot return to its original position despite the action'of spring 23. Thus the key remains partly depressed and this serves as an indicator to show which setting is in use. When another key is depressed it forces down the member Hi again and this, engaging the upper face of the part l5 associated with the already depressed key Ma, forces the member' l5a downso that the cam 19 again engages roller 20 thus again forcing back member l5a until [5 is clear from under l6 and the previously depressed key M is released, the parts associated therewith returning to their original. positions. The part I5 is provided with a bevelled face 24 so that when part I5 is below part l6 and is forced down on depression of another key, it will release, when member l5a is forced back, before member I 5a associated with said other key, and whose part I5 is above the part It, can release. The spring 2| can be omitted if the restoring force applied through strip 22 is sufiicient.

Automatic Wave-band switching, whereby either of two wave bands is selected appropriately for each individual station .key, can also be provided. In Fig. 1 a wave change switch (not shown) is operated by rotation of a shaft 25, to which are keyed two levers 2B, 21, carrying bars 28, 29, which run the whole length of the mechanism. Each of the levers I 411 carries a downwardly projecting member which may be either in the position shown in full lines at 30 or in the position shown in dotted lines at 30a according to which of the two positions of the wave change I switch is required for the operating key in question. Since a member at 30 will obviously have a longer downward travel than one at 30a, owing to the great distance from the pivot 3|, the arm 21 is made correspondingly longer than the arm 26.

As will now be seen all that it is necessary to do to select one of the tuning positions (including adjustment of the wave range switch), is to press the appropriate key M and hold it down until the in the appropriate manner, the remainder of the mechanism being unaltered. Examples of pos-' sible sequences of selector keys are alphabetical,

geographical or in accordance with a pre-arranged time/frequency schedule for a communication service.

Preferably means may be provided to hold the receiver inoperative to reproduce while a tuning operation is in progress. Similarly, means may, if desired, be provided to operate an indicator to show the operator when a tuning operation has been completed.

Where 'the'number' of "selectable tuning' positions required is large,- it may not always be convenient to'arrange all the stop carrying levers ina single line. In such a case they may' be arranged in several banks, each bank having the ends of its stop levers along a line at a difierent angular position about the shaft I, all the operating keys in all the banks, however, acting on common mechanisms for rotating the shaft I to datum point and actuating the wave change switch.

Preferably means are provided to allow of manual tuning when desired, Fig. 2 showing a preferred arrangement. For this purpose two operating keys l4 and I4" which may be marked manual and automatic respectively are provided. Each of these keys has pivotally attached to it a member l5 a with an upper arm l5 shaped as shown in Fig. 1 to engage the upper face l6 of bar I1, similar in every way to'the station selecting key. Thus, upon depression of either key l4 or I4 the shaft l and hence drum 2 are rotated to the datum position. It is to. be understood, however, that the manual and automatic keys I4 and I4 are not provided with stop members 9. A rocker arm 5|, 52 pivoted at 50 and provided with two extensions Md, 1411 is suitably arranged with the keys l4 and I4" so that depression of key I4 will cause the rocker arm to move a forked lever 32 to the left whereas depression of key l4 will cause the rocker arm to move the fork 32 back to its right-hand position, as shown. For this purpose, the lever l4b associated with I4 is provided with an extension Me which acts upon a cam surface on the lefthand end of lever l4d in such a way that depression of key l4 moves the lever l4d over to the right from the position shown. The key I4" is provided with a somewhat similar extension Me which acts upon the cam surface formed on the end of the right-hand portion of lever Md. The upper portion 5| of the rocker i provided with a suitable clamping means 53 which engages the forked lever 32 so that the forked lever is moved in accordance with movements of the rocker 5|, 52. The forked lever 32 engages a grooves collar 33 which is attached to a gearwheel 34. Thus, the forked lever 32 when displaced causes the gear-wheel 34 to be shifted along its axis which is in line with the shaft I. The gear wheel 34 is driven by and slidable with respect to a pinion 35 on a shaft 36 which can be'rotated by a manual tuning knob 31. When the key marked manual i depressed, the shaft l and drum 2 are rotated to the datum position by a mechanism as shown in Fig. 1 and the gear wheel 34 is moved towards the drum 2 by the mechanism 32, 33 so as to bring a stop 38, attached to the gear wheel 34, into a position in which it will engage with the last abutment member 4 on the drum. The spring bias on the drum will, of course, cause the member 4 to press against the stop 38 so that the drum will rotate with the gear wheel 34 in whichever direction the latter is'rotated by means of the knob 31. Since the relative positions of the drum 2 and gear wheel 34 prior to the engagement of manual control may sometimes be such that the abutment member 4 is initially on the Wrong side of the stop 38, this stop is hinged against a light spring 39 so that the abutment member 4 may travel past it when moving towards the datum position, but not in the reverse sense since the stop 38 is prevented from hinging'in the opposite direction by a block 40.

I claim? 1: In" a. preselective tuning mechanism" for a radio receiver or'tlielika-aplurality of abutment members' fastwith the-*tuning-member of the receiver, "a-pliiralitypf cooperating stop members individually movable 'intoand out of the paths of said abutment members, said stop members and abutment members being in such mutual relationship that the permissible movement of the tuning member away from a datum position can be selected at any of a plurality of predetermined amounts by selecting an appropriate stop member to be moved into the path of its cooperating abutment member, means for biasing said tuning member away from said datum position, selector members for selecting any stop member to be moved into the path of the cooperating stop member, means actuated upon operation of any of the selector members for moving said tuning'member to its datum position and then releasing it to move under its bias until it is stopped by the selected stop member, and means for retaining any abutment member and cooperating stop member which have engaged one another in such engagement until a fresh tuning operation is initiated.

2. In a preselective tuning mechanism for a radio receiver or the like, a variable tuning member, a drum-like element operable with the tuning member, a plurality of adjustable abutment members disposed on said drum-like member, a corresponding number of cooperating stop members individually movable into and out of the paths of said abutment members, said stop members and abutment members being in such mutual relationship that the permissible movement of the tuning member away from a predetermined datum position can be selected to any of a plurality of predetermined amounts by selecting an appropriate stop member to be moved into the path of its cooperating abutment member, means for biasing said tuning member away from said datum position, selectively operable selector members for selecting any stop member to be moved into the path of its cooperating abutment member, means actuated upon operation of any of the selector members, for moving the tuningmember first to its datum position and then for releasing it to move under its bias until it is stopped by the engagement of the selected stop member with its cooperating abutment member, means for retaining any abutment member and cooperating stop member which have engaged one another in such engagement until a new tuning operation is initiated, and means for retaining the last operated selector member in a position which serves as an indicator to show which setting of the tuning member is in use.

3. In a preselective tuning mechanism as described in the next preceding claim and wherein the radio receiver is provided with an operable wave change switch, means cooperating with at least one of the selector members for automatically operating said operable wave change switch upon actuation of said selector member tothereby adjust the wave change switch to the position corresponding to the wave range within which the station arranged to be selected by said selector member lies.

4. In an arrangement as described in claim 2, means for rendering the last named means inoperative to retain the last operated selector member in said indicating position upon operation of another of said selector members.

5. In an arrangement as described in claim 2,

a. normally inoperative driving mechanism for the tuning member of the radio receiver, an additional operable selector member acting upon selective operation thereof for moving the timing member first to its datum position and then for releasing it to move under its bias to a position which locks it with said driving mechanism and thereby render said driving mechanism operative, and means acting upon operation of said additional selector member for releasing any previously operated selective member.

DAVID ARTHUR BELL. 

